drivers/vhost/vringh.c

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This source file includes following definitions.
__printf
__vringh_get_head
vringh_iov_xfer
range_check
no_range_check
move_to_indirect
resize_iovec
return_from_indirect
slow_copy
__vringh_iov
__vringh_complete
__vringh_need_notify
__vringh_notify_enable
__vringh_notify_disable
getu16_user
putu16_user
copydesc_user
putused_user
xfer_from_user
xfer_to_user
vringh_init_user
vringh_getdesc_user
vringh_iov_pull_user
vringh_iov_push_user
vringh_abandon_user
vringh_complete_user
vringh_complete_multi_user
vringh_notify_enable_user
vringh_notify_disable_user
vringh_need_notify_user
getu16_kern
putu16_kern
copydesc_kern
putused_kern
xfer_kern
kern_xfer
vringh_init_kern
vringh_getdesc_kern
vringh_iov_pull_kern
vringh_iov_push_kern
vringh_abandon_kern
vringh_complete_kern
vringh_notify_enable_kern
vringh_notify_disable_kern
vringh_need_notify_kern
   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Helpers for the host side of a virtio ring.
   4  *
   5  * Since these may be in userspace, we use (inline) accessors.
   6  */
   7 #include <linux/compiler.h>
   8 #include <linux/module.h>
   9 #include <linux/vringh.h>
  10 #include <linux/virtio_ring.h>
  11 #include <linux/kernel.h>
  12 #include <linux/ratelimit.h>
  13 #include <linux/uaccess.h>
  14 #include <linux/slab.h>
  15 #include <linux/export.h>
  16 #include <uapi/linux/virtio_config.h>
  17 
  18 static __printf(1,2) __cold void vringh_bad(const char *fmt, ...)
  19 {
  20         static DEFINE_RATELIMIT_STATE(vringh_rs,
  21                                       DEFAULT_RATELIMIT_INTERVAL,
  22                                       DEFAULT_RATELIMIT_BURST);
  23         if (__ratelimit(&vringh_rs)) {
  24                 va_list ap;
  25                 va_start(ap, fmt);
  26                 printk(KERN_NOTICE "vringh:");
  27                 vprintk(fmt, ap);
  28                 va_end(ap);
  29         }
  30 }
  31 
  32 /* Returns vring->num if empty, -ve on error. */
  33 static inline int __vringh_get_head(const struct vringh *vrh,
  34                                     int (*getu16)(const struct vringh *vrh,
  35                                                   u16 *val, const __virtio16 *p),
  36                                     u16 *last_avail_idx)
  37 {
  38         u16 avail_idx, i, head;
  39         int err;
  40 
  41         err = getu16(vrh, &avail_idx, &vrh->vring.avail->idx);
  42         if (err) {
  43                 vringh_bad("Failed to access avail idx at %p",
  44                            &vrh->vring.avail->idx);
  45                 return err;
  46         }
  47 
  48         if (*last_avail_idx == avail_idx)
  49                 return vrh->vring.num;
  50 
  51         /* Only get avail ring entries after they have been exposed by guest. */
  52         virtio_rmb(vrh->weak_barriers);
  53 
  54         i = *last_avail_idx & (vrh->vring.num - 1);
  55 
  56         err = getu16(vrh, &head, &vrh->vring.avail->ring[i]);
  57         if (err) {
  58                 vringh_bad("Failed to read head: idx %d address %p",
  59                            *last_avail_idx, &vrh->vring.avail->ring[i]);
  60                 return err;
  61         }
  62 
  63         if (head >= vrh->vring.num) {
  64                 vringh_bad("Guest says index %u > %u is available",
  65                            head, vrh->vring.num);
  66                 return -EINVAL;
  67         }
  68 
  69         (*last_avail_idx)++;
  70         return head;
  71 }
  72 
  73 /* Copy some bytes to/from the iovec.  Returns num copied. */
  74 static inline ssize_t vringh_iov_xfer(struct vringh_kiov *iov,
  75                                       void *ptr, size_t len,
  76                                       int (*xfer)(void *addr, void *ptr,
  77                                                   size_t len))
  78 {
  79         int err, done = 0;
  80 
  81         while (len && iov->i < iov->used) {
  82                 size_t partlen;
  83 
  84                 partlen = min(iov->iov[iov->i].iov_len, len);
  85                 err = xfer(iov->iov[iov->i].iov_base, ptr, partlen);
  86                 if (err)
  87                         return err;
  88                 done += partlen;
  89                 len -= partlen;
  90                 ptr += partlen;
  91                 iov->consumed += partlen;
  92                 iov->iov[iov->i].iov_len -= partlen;
  93                 iov->iov[iov->i].iov_base += partlen;
  94 
  95                 if (!iov->iov[iov->i].iov_len) {
  96                         /* Fix up old iov element then increment. */
  97                         iov->iov[iov->i].iov_len = iov->consumed;
  98                         iov->iov[iov->i].iov_base -= iov->consumed;
  99                         
 100                         iov->consumed = 0;
 101                         iov->i++;
 102                 }
 103         }
 104         return done;
 105 }
 106 
 107 /* May reduce *len if range is shorter. */
 108 static inline bool range_check(struct vringh *vrh, u64 addr, size_t *len,
 109                                struct vringh_range *range,
 110                                bool (*getrange)(struct vringh *,
 111                                                 u64, struct vringh_range *))
 112 {
 113         if (addr < range->start || addr > range->end_incl) {
 114                 if (!getrange(vrh, addr, range))
 115                         return false;
 116         }
 117         BUG_ON(addr < range->start || addr > range->end_incl);
 118 
 119         /* To end of memory? */
 120         if (unlikely(addr + *len == 0)) {
 121                 if (range->end_incl == -1ULL)
 122                         return true;
 123                 goto truncate;
 124         }
 125 
 126         /* Otherwise, don't wrap. */
 127         if (addr + *len < addr) {
 128                 vringh_bad("Wrapping descriptor %zu@0x%llx",
 129                            *len, (unsigned long long)addr);
 130                 return false;
 131         }
 132 
 133         if (unlikely(addr + *len - 1 > range->end_incl))
 134                 goto truncate;
 135         return true;
 136 
 137 truncate:
 138         *len = range->end_incl + 1 - addr;
 139         return true;
 140 }
 141 
 142 static inline bool no_range_check(struct vringh *vrh, u64 addr, size_t *len,
 143                                   struct vringh_range *range,
 144                                   bool (*getrange)(struct vringh *,
 145                                                    u64, struct vringh_range *))
 146 {
 147         return true;
 148 }
 149 
 150 /* No reason for this code to be inline. */
 151 static int move_to_indirect(const struct vringh *vrh,
 152                             int *up_next, u16 *i, void *addr,
 153                             const struct vring_desc *desc,
 154                             struct vring_desc **descs, int *desc_max)
 155 {
 156         u32 len;
 157 
 158         /* Indirect tables can't have indirect. */
 159         if (*up_next != -1) {
 160                 vringh_bad("Multilevel indirect %u->%u", *up_next, *i);
 161                 return -EINVAL;
 162         }
 163 
 164         len = vringh32_to_cpu(vrh, desc->len);
 165         if (unlikely(len % sizeof(struct vring_desc))) {
 166                 vringh_bad("Strange indirect len %u", desc->len);
 167                 return -EINVAL;
 168         }
 169 
 170         /* We will check this when we follow it! */
 171         if (desc->flags & cpu_to_vringh16(vrh, VRING_DESC_F_NEXT))
 172                 *up_next = vringh16_to_cpu(vrh, desc->next);
 173         else
 174                 *up_next = -2;
 175         *descs = addr;
 176         *desc_max = len / sizeof(struct vring_desc);
 177 
 178         /* Now, start at the first indirect. */
 179         *i = 0;
 180         return 0;
 181 }
 182 
 183 static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
 184 {
 185         struct kvec *new;
 186         unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
 187 
 188         if (new_num < 8)
 189                 new_num = 8;
 190 
 191         flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
 192         if (flag)
 193                 new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
 194         else {
 195                 new = kmalloc_array(new_num, sizeof(struct iovec), gfp);
 196                 if (new) {
 197                         memcpy(new, iov->iov,
 198                                iov->max_num * sizeof(struct iovec));
 199                         flag = VRINGH_IOV_ALLOCATED;
 200                 }
 201         }
 202         if (!new)
 203                 return -ENOMEM;
 204         iov->iov = new;
 205         iov->max_num = (new_num | flag);
 206         return 0;
 207 }
 208 
 209 static u16 __cold return_from_indirect(const struct vringh *vrh, int *up_next,
 210                                        struct vring_desc **descs, int *desc_max)
 211 {
 212         u16 i = *up_next;
 213 
 214         *up_next = -1;
 215         *descs = vrh->vring.desc;
 216         *desc_max = vrh->vring.num;
 217         return i;
 218 }
 219 
 220 static int slow_copy(struct vringh *vrh, void *dst, const void *src,
 221                      bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
 222                                     struct vringh_range *range,
 223                                     bool (*getrange)(struct vringh *vrh,
 224                                                      u64,
 225                                                      struct vringh_range *)),
 226                      bool (*getrange)(struct vringh *vrh,
 227                                       u64 addr,
 228                                       struct vringh_range *r),
 229                      struct vringh_range *range,
 230                      int (*copy)(void *dst, const void *src, size_t len))
 231 {
 232         size_t part, len = sizeof(struct vring_desc);
 233 
 234         do {
 235                 u64 addr;
 236                 int err;
 237 
 238                 part = len;
 239                 addr = (u64)(unsigned long)src - range->offset;
 240 
 241                 if (!rcheck(vrh, addr, &part, range, getrange))
 242                         return -EINVAL;
 243 
 244                 err = copy(dst, src, part);
 245                 if (err)
 246                         return err;
 247 
 248                 dst += part;
 249                 src += part;
 250                 len -= part;
 251         } while (len);
 252         return 0;
 253 }
 254 
 255 static inline int
 256 __vringh_iov(struct vringh *vrh, u16 i,
 257              struct vringh_kiov *riov,
 258              struct vringh_kiov *wiov,
 259              bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
 260                             struct vringh_range *range,
 261                             bool (*getrange)(struct vringh *, u64,
 262                                              struct vringh_range *)),
 263              bool (*getrange)(struct vringh *, u64, struct vringh_range *),
 264              gfp_t gfp,
 265              int (*copy)(void *dst, const void *src, size_t len))
 266 {
 267         int err, count = 0, up_next, desc_max;
 268         struct vring_desc desc, *descs;
 269         struct vringh_range range = { -1ULL, 0 }, slowrange;
 270         bool slow = false;
 271 
 272         /* We start traversing vring's descriptor table. */
 273         descs = vrh->vring.desc;
 274         desc_max = vrh->vring.num;
 275         up_next = -1;
 276 
 277         if (riov)
 278                 riov->i = riov->used = 0;
 279         else if (wiov)
 280                 wiov->i = wiov->used = 0;
 281         else
 282                 /* You must want something! */
 283                 BUG();
 284 
 285         for (;;) {
 286                 void *addr;
 287                 struct vringh_kiov *iov;
 288                 size_t len;
 289 
 290                 if (unlikely(slow))
 291                         err = slow_copy(vrh, &desc, &descs[i], rcheck, getrange,
 292                                         &slowrange, copy);
 293                 else
 294                         err = copy(&desc, &descs[i], sizeof(desc));
 295                 if (unlikely(err))
 296                         goto fail;
 297 
 298                 if (unlikely(desc.flags &
 299                              cpu_to_vringh16(vrh, VRING_DESC_F_INDIRECT))) {
 300                         u64 a = vringh64_to_cpu(vrh, desc.addr);
 301 
 302                         /* Make sure it's OK, and get offset. */
 303                         len = vringh32_to_cpu(vrh, desc.len);
 304                         if (!rcheck(vrh, a, &len, &range, getrange)) {
 305                                 err = -EINVAL;
 306                                 goto fail;
 307                         }
 308 
 309                         if (unlikely(len != vringh32_to_cpu(vrh, desc.len))) {
 310                                 slow = true;
 311                                 /* We need to save this range to use offset */
 312                                 slowrange = range;
 313                         }
 314 
 315                         addr = (void *)(long)(a + range.offset);
 316                         err = move_to_indirect(vrh, &up_next, &i, addr, &desc,
 317                                                &descs, &desc_max);
 318                         if (err)
 319                                 goto fail;
 320                         continue;
 321                 }
 322 
 323                 if (count++ == vrh->vring.num) {
 324                         vringh_bad("Descriptor loop in %p", descs);
 325                         err = -ELOOP;
 326                         goto fail;
 327                 }
 328 
 329                 if (desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_WRITE))
 330                         iov = wiov;
 331                 else {
 332                         iov = riov;
 333                         if (unlikely(wiov && wiov->i)) {
 334                                 vringh_bad("Readable desc %p after writable",
 335                                            &descs[i]);
 336                                 err = -EINVAL;
 337                                 goto fail;
 338                         }
 339                 }
 340 
 341                 if (!iov) {
 342                         vringh_bad("Unexpected %s desc",
 343                                    !wiov ? "writable" : "readable");
 344                         err = -EPROTO;
 345                         goto fail;
 346                 }
 347 
 348         again:
 349                 /* Make sure it's OK, and get offset. */
 350                 len = vringh32_to_cpu(vrh, desc.len);
 351                 if (!rcheck(vrh, vringh64_to_cpu(vrh, desc.addr), &len, &range,
 352                             getrange)) {
 353                         err = -EINVAL;
 354                         goto fail;
 355                 }
 356                 addr = (void *)(unsigned long)(vringh64_to_cpu(vrh, desc.addr) +
 357                                                range.offset);
 358 
 359                 if (unlikely(iov->used == (iov->max_num & ~VRINGH_IOV_ALLOCATED))) {
 360                         err = resize_iovec(iov, gfp);
 361                         if (err)
 362                                 goto fail;
 363                 }
 364 
 365                 iov->iov[iov->used].iov_base = addr;
 366                 iov->iov[iov->used].iov_len = len;
 367                 iov->used++;
 368 
 369                 if (unlikely(len != vringh32_to_cpu(vrh, desc.len))) {
 370                         desc.len = cpu_to_vringh32(vrh,
 371                                    vringh32_to_cpu(vrh, desc.len) - len);
 372                         desc.addr = cpu_to_vringh64(vrh,
 373                                     vringh64_to_cpu(vrh, desc.addr) + len);
 374                         goto again;
 375                 }
 376 
 377                 if (desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_NEXT)) {
 378                         i = vringh16_to_cpu(vrh, desc.next);
 379                 } else {
 380                         /* Just in case we need to finish traversing above. */
 381                         if (unlikely(up_next > 0)) {
 382                                 i = return_from_indirect(vrh, &up_next,
 383                                                          &descs, &desc_max);
 384                                 slow = false;
 385                         } else
 386                                 break;
 387                 }
 388 
 389                 if (i >= desc_max) {
 390                         vringh_bad("Chained index %u > %u", i, desc_max);
 391                         err = -EINVAL;
 392                         goto fail;
 393                 }
 394         }
 395 
 396         return 0;
 397 
 398 fail:
 399         return err;
 400 }
 401 
 402 static inline int __vringh_complete(struct vringh *vrh,
 403                                     const struct vring_used_elem *used,
 404                                     unsigned int num_used,
 405                                     int (*putu16)(const struct vringh *vrh,
 406                                                   __virtio16 *p, u16 val),
 407                                     int (*putused)(struct vring_used_elem *dst,
 408                                                    const struct vring_used_elem
 409                                                    *src, unsigned num))
 410 {
 411         struct vring_used *used_ring;
 412         int err;
 413         u16 used_idx, off;
 414 
 415         used_ring = vrh->vring.used;
 416         used_idx = vrh->last_used_idx + vrh->completed;
 417 
 418         off = used_idx % vrh->vring.num;
 419 
 420         /* Compiler knows num_used == 1 sometimes, hence extra check */
 421         if (num_used > 1 && unlikely(off + num_used >= vrh->vring.num)) {
 422                 u16 part = vrh->vring.num - off;
 423                 err = putused(&used_ring->ring[off], used, part);
 424                 if (!err)
 425                         err = putused(&used_ring->ring[0], used + part,
 426                                       num_used - part);
 427         } else
 428                 err = putused(&used_ring->ring[off], used, num_used);
 429 
 430         if (err) {
 431                 vringh_bad("Failed to write %u used entries %u at %p",
 432                            num_used, off, &used_ring->ring[off]);
 433                 return err;
 434         }
 435 
 436         /* Make sure buffer is written before we update index. */
 437         virtio_wmb(vrh->weak_barriers);
 438 
 439         err = putu16(vrh, &vrh->vring.used->idx, used_idx + num_used);
 440         if (err) {
 441                 vringh_bad("Failed to update used index at %p",
 442                            &vrh->vring.used->idx);
 443                 return err;
 444         }
 445 
 446         vrh->completed += num_used;
 447         return 0;
 448 }
 449 
 450 
 451 static inline int __vringh_need_notify(struct vringh *vrh,
 452                                        int (*getu16)(const struct vringh *vrh,
 453                                                      u16 *val,
 454                                                      const __virtio16 *p))
 455 {
 456         bool notify;
 457         u16 used_event;
 458         int err;
 459 
 460         /* Flush out used index update. This is paired with the
 461          * barrier that the Guest executes when enabling
 462          * interrupts. */
 463         virtio_mb(vrh->weak_barriers);
 464 
 465         /* Old-style, without event indices. */
 466         if (!vrh->event_indices) {
 467                 u16 flags;
 468                 err = getu16(vrh, &flags, &vrh->vring.avail->flags);
 469                 if (err) {
 470                         vringh_bad("Failed to get flags at %p",
 471                                    &vrh->vring.avail->flags);
 472                         return err;
 473                 }
 474                 return (!(flags & VRING_AVAIL_F_NO_INTERRUPT));
 475         }
 476 
 477         /* Modern: we know when other side wants to know. */
 478         err = getu16(vrh, &used_event, &vring_used_event(&vrh->vring));
 479         if (err) {
 480                 vringh_bad("Failed to get used event idx at %p",
 481                            &vring_used_event(&vrh->vring));
 482                 return err;
 483         }
 484 
 485         /* Just in case we added so many that we wrap. */
 486         if (unlikely(vrh->completed > 0xffff))
 487                 notify = true;
 488         else
 489                 notify = vring_need_event(used_event,
 490                                           vrh->last_used_idx + vrh->completed,
 491                                           vrh->last_used_idx);
 492 
 493         vrh->last_used_idx += vrh->completed;
 494         vrh->completed = 0;
 495         return notify;
 496 }
 497 
 498 static inline bool __vringh_notify_enable(struct vringh *vrh,
 499                                           int (*getu16)(const struct vringh *vrh,
 500                                                         u16 *val, const __virtio16 *p),
 501                                           int (*putu16)(const struct vringh *vrh,
 502                                                         __virtio16 *p, u16 val))
 503 {
 504         u16 avail;
 505 
 506         if (!vrh->event_indices) {
 507                 /* Old-school; update flags. */
 508                 if (putu16(vrh, &vrh->vring.used->flags, 0) != 0) {
 509                         vringh_bad("Clearing used flags %p",
 510                                    &vrh->vring.used->flags);
 511                         return true;
 512                 }
 513         } else {
 514                 if (putu16(vrh, &vring_avail_event(&vrh->vring),
 515                            vrh->last_avail_idx) != 0) {
 516                         vringh_bad("Updating avail event index %p",
 517                                    &vring_avail_event(&vrh->vring));
 518                         return true;
 519                 }
 520         }
 521 
 522         /* They could have slipped one in as we were doing that: make
 523          * sure it's written, then check again. */
 524         virtio_mb(vrh->weak_barriers);
 525 
 526         if (getu16(vrh, &avail, &vrh->vring.avail->idx) != 0) {
 527                 vringh_bad("Failed to check avail idx at %p",
 528                            &vrh->vring.avail->idx);
 529                 return true;
 530         }
 531 
 532         /* This is unlikely, so we just leave notifications enabled
 533          * (if we're using event_indices, we'll only get one
 534          * notification anyway). */
 535         return avail == vrh->last_avail_idx;
 536 }
 537 
 538 static inline void __vringh_notify_disable(struct vringh *vrh,
 539                                            int (*putu16)(const struct vringh *vrh,
 540                                                          __virtio16 *p, u16 val))
 541 {
 542         if (!vrh->event_indices) {
 543                 /* Old-school; update flags. */
 544                 if (putu16(vrh, &vrh->vring.used->flags,
 545                            VRING_USED_F_NO_NOTIFY)) {
 546                         vringh_bad("Setting used flags %p",
 547                                    &vrh->vring.used->flags);
 548                 }
 549         }
 550 }
 551 
 552 /* Userspace access helpers: in this case, addresses are really userspace. */
 553 static inline int getu16_user(const struct vringh *vrh, u16 *val, const __virtio16 *p)
 554 {
 555         __virtio16 v = 0;
 556         int rc = get_user(v, (__force __virtio16 __user *)p);
 557         *val = vringh16_to_cpu(vrh, v);
 558         return rc;
 559 }
 560 
 561 static inline int putu16_user(const struct vringh *vrh, __virtio16 *p, u16 val)
 562 {
 563         __virtio16 v = cpu_to_vringh16(vrh, val);
 564         return put_user(v, (__force __virtio16 __user *)p);
 565 }
 566 
 567 static inline int copydesc_user(void *dst, const void *src, size_t len)
 568 {
 569         return copy_from_user(dst, (__force void __user *)src, len) ?
 570                 -EFAULT : 0;
 571 }
 572 
 573 static inline int putused_user(struct vring_used_elem *dst,
 574                                const struct vring_used_elem *src,
 575                                unsigned int num)
 576 {
 577         return copy_to_user((__force void __user *)dst, src,
 578                             sizeof(*dst) * num) ? -EFAULT : 0;
 579 }
 580 
 581 static inline int xfer_from_user(void *src, void *dst, size_t len)
 582 {
 583         return copy_from_user(dst, (__force void __user *)src, len) ?
 584                 -EFAULT : 0;
 585 }
 586 
 587 static inline int xfer_to_user(void *dst, void *src, size_t len)
 588 {
 589         return copy_to_user((__force void __user *)dst, src, len) ?
 590                 -EFAULT : 0;
 591 }
 592 
 593 /**
 594  * vringh_init_user - initialize a vringh for a userspace vring.
 595  * @vrh: the vringh to initialize.
 596  * @features: the feature bits for this ring.
 597  * @num: the number of elements.
 598  * @weak_barriers: true if we only need memory barriers, not I/O.
 599  * @desc: the userpace descriptor pointer.
 600  * @avail: the userpace avail pointer.
 601  * @used: the userpace used pointer.
 602  *
 603  * Returns an error if num is invalid: you should check pointers
 604  * yourself!
 605  */
 606 int vringh_init_user(struct vringh *vrh, u64 features,
 607                      unsigned int num, bool weak_barriers,
 608                      struct vring_desc __user *desc,
 609                      struct vring_avail __user *avail,
 610                      struct vring_used __user *used)
 611 {
 612         /* Sane power of 2 please! */
 613         if (!num || num > 0xffff || (num & (num - 1))) {
 614                 vringh_bad("Bad ring size %u", num);
 615                 return -EINVAL;
 616         }
 617 
 618         vrh->little_endian = (features & (1ULL << VIRTIO_F_VERSION_1));
 619         vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
 620         vrh->weak_barriers = weak_barriers;
 621         vrh->completed = 0;
 622         vrh->last_avail_idx = 0;
 623         vrh->last_used_idx = 0;
 624         vrh->vring.num = num;
 625         /* vring expects kernel addresses, but only used via accessors. */
 626         vrh->vring.desc = (__force struct vring_desc *)desc;
 627         vrh->vring.avail = (__force struct vring_avail *)avail;
 628         vrh->vring.used = (__force struct vring_used *)used;
 629         return 0;
 630 }
 631 EXPORT_SYMBOL(vringh_init_user);
 632 
 633 /**
 634  * vringh_getdesc_user - get next available descriptor from userspace ring.
 635  * @vrh: the userspace vring.
 636  * @riov: where to put the readable descriptors (or NULL)
 637  * @wiov: where to put the writable descriptors (or NULL)
 638  * @getrange: function to call to check ranges.
 639  * @head: head index we received, for passing to vringh_complete_user().
 640  *
 641  * Returns 0 if there was no descriptor, 1 if there was, or -errno.
 642  *
 643  * Note that on error return, you can tell the difference between an
 644  * invalid ring and a single invalid descriptor: in the former case,
 645  * *head will be vrh->vring.num.  You may be able to ignore an invalid
 646  * descriptor, but there's not much you can do with an invalid ring.
 647  *
 648  * Note that you may need to clean up riov and wiov, even on error!
 649  */
 650 int vringh_getdesc_user(struct vringh *vrh,
 651                         struct vringh_iov *riov,
 652                         struct vringh_iov *wiov,
 653                         bool (*getrange)(struct vringh *vrh,
 654                                          u64 addr, struct vringh_range *r),
 655                         u16 *head)
 656 {
 657         int err;
 658 
 659         *head = vrh->vring.num;
 660         err = __vringh_get_head(vrh, getu16_user, &vrh->last_avail_idx);
 661         if (err < 0)
 662                 return err;
 663 
 664         /* Empty... */
 665         if (err == vrh->vring.num)
 666                 return 0;
 667 
 668         /* We need the layouts to be the identical for this to work */
 669         BUILD_BUG_ON(sizeof(struct vringh_kiov) != sizeof(struct vringh_iov));
 670         BUILD_BUG_ON(offsetof(struct vringh_kiov, iov) !=
 671                      offsetof(struct vringh_iov, iov));
 672         BUILD_BUG_ON(offsetof(struct vringh_kiov, i) !=
 673                      offsetof(struct vringh_iov, i));
 674         BUILD_BUG_ON(offsetof(struct vringh_kiov, used) !=
 675                      offsetof(struct vringh_iov, used));
 676         BUILD_BUG_ON(offsetof(struct vringh_kiov, max_num) !=
 677                      offsetof(struct vringh_iov, max_num));
 678         BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
 679         BUILD_BUG_ON(offsetof(struct iovec, iov_base) !=
 680                      offsetof(struct kvec, iov_base));
 681         BUILD_BUG_ON(offsetof(struct iovec, iov_len) !=
 682                      offsetof(struct kvec, iov_len));
 683         BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_base)
 684                      != sizeof(((struct kvec *)NULL)->iov_base));
 685         BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_len)
 686                      != sizeof(((struct kvec *)NULL)->iov_len));
 687 
 688         *head = err;
 689         err = __vringh_iov(vrh, *head, (struct vringh_kiov *)riov,
 690                            (struct vringh_kiov *)wiov,
 691                            range_check, getrange, GFP_KERNEL, copydesc_user);
 692         if (err)
 693                 return err;
 694 
 695         return 1;
 696 }
 697 EXPORT_SYMBOL(vringh_getdesc_user);
 698 
 699 /**
 700  * vringh_iov_pull_user - copy bytes from vring_iov.
 701  * @riov: the riov as passed to vringh_getdesc_user() (updated as we consume)
 702  * @dst: the place to copy.
 703  * @len: the maximum length to copy.
 704  *
 705  * Returns the bytes copied <= len or a negative errno.
 706  */
 707 ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len)
 708 {
 709         return vringh_iov_xfer((struct vringh_kiov *)riov,
 710                                dst, len, xfer_from_user);
 711 }
 712 EXPORT_SYMBOL(vringh_iov_pull_user);
 713 
 714 /**
 715  * vringh_iov_push_user - copy bytes into vring_iov.
 716  * @wiov: the wiov as passed to vringh_getdesc_user() (updated as we consume)
 717  * @dst: the place to copy.
 718  * @len: the maximum length to copy.
 719  *
 720  * Returns the bytes copied <= len or a negative errno.
 721  */
 722 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
 723                              const void *src, size_t len)
 724 {
 725         return vringh_iov_xfer((struct vringh_kiov *)wiov,
 726                                (void *)src, len, xfer_to_user);
 727 }
 728 EXPORT_SYMBOL(vringh_iov_push_user);
 729 
 730 /**
 731  * vringh_abandon_user - we've decided not to handle the descriptor(s).
 732  * @vrh: the vring.
 733  * @num: the number of descriptors to put back (ie. num
 734  *       vringh_get_user() to undo).
 735  *
 736  * The next vringh_get_user() will return the old descriptor(s) again.
 737  */
 738 void vringh_abandon_user(struct vringh *vrh, unsigned int num)
 739 {
 740         /* We only update vring_avail_event(vr) when we want to be notified,
 741          * so we haven't changed that yet. */
 742         vrh->last_avail_idx -= num;
 743 }
 744 EXPORT_SYMBOL(vringh_abandon_user);
 745 
 746 /**
 747  * vringh_complete_user - we've finished with descriptor, publish it.
 748  * @vrh: the vring.
 749  * @head: the head as filled in by vringh_getdesc_user.
 750  * @len: the length of data we have written.
 751  *
 752  * You should check vringh_need_notify_user() after one or more calls
 753  * to this function.
 754  */
 755 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len)
 756 {
 757         struct vring_used_elem used;
 758 
 759         used.id = cpu_to_vringh32(vrh, head);
 760         used.len = cpu_to_vringh32(vrh, len);
 761         return __vringh_complete(vrh, &used, 1, putu16_user, putused_user);
 762 }
 763 EXPORT_SYMBOL(vringh_complete_user);
 764 
 765 /**
 766  * vringh_complete_multi_user - we've finished with many descriptors.
 767  * @vrh: the vring.
 768  * @used: the head, length pairs.
 769  * @num_used: the number of used elements.
 770  *
 771  * You should check vringh_need_notify_user() after one or more calls
 772  * to this function.
 773  */
 774 int vringh_complete_multi_user(struct vringh *vrh,
 775                                const struct vring_used_elem used[],
 776                                unsigned num_used)
 777 {
 778         return __vringh_complete(vrh, used, num_used,
 779                                  putu16_user, putused_user);
 780 }
 781 EXPORT_SYMBOL(vringh_complete_multi_user);
 782 
 783 /**
 784  * vringh_notify_enable_user - we want to know if something changes.
 785  * @vrh: the vring.
 786  *
 787  * This always enables notifications, but returns false if there are
 788  * now more buffers available in the vring.
 789  */
 790 bool vringh_notify_enable_user(struct vringh *vrh)
 791 {
 792         return __vringh_notify_enable(vrh, getu16_user, putu16_user);
 793 }
 794 EXPORT_SYMBOL(vringh_notify_enable_user);
 795 
 796 /**
 797  * vringh_notify_disable_user - don't tell us if something changes.
 798  * @vrh: the vring.
 799  *
 800  * This is our normal running state: we disable and then only enable when
 801  * we're going to sleep.
 802  */
 803 void vringh_notify_disable_user(struct vringh *vrh)
 804 {
 805         __vringh_notify_disable(vrh, putu16_user);
 806 }
 807 EXPORT_SYMBOL(vringh_notify_disable_user);
 808 
 809 /**
 810  * vringh_need_notify_user - must we tell the other side about used buffers?
 811  * @vrh: the vring we've called vringh_complete_user() on.
 812  *
 813  * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
 814  */
 815 int vringh_need_notify_user(struct vringh *vrh)
 816 {
 817         return __vringh_need_notify(vrh, getu16_user);
 818 }
 819 EXPORT_SYMBOL(vringh_need_notify_user);
 820 
 821 /* Kernelspace access helpers. */
 822 static inline int getu16_kern(const struct vringh *vrh,
 823                               u16 *val, const __virtio16 *p)
 824 {
 825         *val = vringh16_to_cpu(vrh, READ_ONCE(*p));
 826         return 0;
 827 }
 828 
 829 static inline int putu16_kern(const struct vringh *vrh, __virtio16 *p, u16 val)
 830 {
 831         WRITE_ONCE(*p, cpu_to_vringh16(vrh, val));
 832         return 0;
 833 }
 834 
 835 static inline int copydesc_kern(void *dst, const void *src, size_t len)
 836 {
 837         memcpy(dst, src, len);
 838         return 0;
 839 }
 840 
 841 static inline int putused_kern(struct vring_used_elem *dst,
 842                                const struct vring_used_elem *src,
 843                                unsigned int num)
 844 {
 845         memcpy(dst, src, num * sizeof(*dst));
 846         return 0;
 847 }
 848 
 849 static inline int xfer_kern(void *src, void *dst, size_t len)
 850 {
 851         memcpy(dst, src, len);
 852         return 0;
 853 }
 854 
 855 static inline int kern_xfer(void *dst, void *src, size_t len)
 856 {
 857         memcpy(dst, src, len);
 858         return 0;
 859 }
 860 
 861 /**
 862  * vringh_init_kern - initialize a vringh for a kernelspace vring.
 863  * @vrh: the vringh to initialize.
 864  * @features: the feature bits for this ring.
 865  * @num: the number of elements.
 866  * @weak_barriers: true if we only need memory barriers, not I/O.
 867  * @desc: the userpace descriptor pointer.
 868  * @avail: the userpace avail pointer.
 869  * @used: the userpace used pointer.
 870  *
 871  * Returns an error if num is invalid.
 872  */
 873 int vringh_init_kern(struct vringh *vrh, u64 features,
 874                      unsigned int num, bool weak_barriers,
 875                      struct vring_desc *desc,
 876                      struct vring_avail *avail,
 877                      struct vring_used *used)
 878 {
 879         /* Sane power of 2 please! */
 880         if (!num || num > 0xffff || (num & (num - 1))) {
 881                 vringh_bad("Bad ring size %u", num);
 882                 return -EINVAL;
 883         }
 884 
 885         vrh->little_endian = (features & (1ULL << VIRTIO_F_VERSION_1));
 886         vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
 887         vrh->weak_barriers = weak_barriers;
 888         vrh->completed = 0;
 889         vrh->last_avail_idx = 0;
 890         vrh->last_used_idx = 0;
 891         vrh->vring.num = num;
 892         vrh->vring.desc = desc;
 893         vrh->vring.avail = avail;
 894         vrh->vring.used = used;
 895         return 0;
 896 }
 897 EXPORT_SYMBOL(vringh_init_kern);
 898 
 899 /**
 900  * vringh_getdesc_kern - get next available descriptor from kernelspace ring.
 901  * @vrh: the kernelspace vring.
 902  * @riov: where to put the readable descriptors (or NULL)
 903  * @wiov: where to put the writable descriptors (or NULL)
 904  * @head: head index we received, for passing to vringh_complete_kern().
 905  * @gfp: flags for allocating larger riov/wiov.
 906  *
 907  * Returns 0 if there was no descriptor, 1 if there was, or -errno.
 908  *
 909  * Note that on error return, you can tell the difference between an
 910  * invalid ring and a single invalid descriptor: in the former case,
 911  * *head will be vrh->vring.num.  You may be able to ignore an invalid
 912  * descriptor, but there's not much you can do with an invalid ring.
 913  *
 914  * Note that you may need to clean up riov and wiov, even on error!
 915  */
 916 int vringh_getdesc_kern(struct vringh *vrh,
 917                         struct vringh_kiov *riov,
 918                         struct vringh_kiov *wiov,
 919                         u16 *head,
 920                         gfp_t gfp)
 921 {
 922         int err;
 923 
 924         err = __vringh_get_head(vrh, getu16_kern, &vrh->last_avail_idx);
 925         if (err < 0)
 926                 return err;
 927 
 928         /* Empty... */
 929         if (err == vrh->vring.num)
 930                 return 0;
 931 
 932         *head = err;
 933         err = __vringh_iov(vrh, *head, riov, wiov, no_range_check, NULL,
 934                            gfp, copydesc_kern);
 935         if (err)
 936                 return err;
 937 
 938         return 1;
 939 }
 940 EXPORT_SYMBOL(vringh_getdesc_kern);
 941 
 942 /**
 943  * vringh_iov_pull_kern - copy bytes from vring_iov.
 944  * @riov: the riov as passed to vringh_getdesc_kern() (updated as we consume)
 945  * @dst: the place to copy.
 946  * @len: the maximum length to copy.
 947  *
 948  * Returns the bytes copied <= len or a negative errno.
 949  */
 950 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len)
 951 {
 952         return vringh_iov_xfer(riov, dst, len, xfer_kern);
 953 }
 954 EXPORT_SYMBOL(vringh_iov_pull_kern);
 955 
 956 /**
 957  * vringh_iov_push_kern - copy bytes into vring_iov.
 958  * @wiov: the wiov as passed to vringh_getdesc_kern() (updated as we consume)
 959  * @dst: the place to copy.
 960  * @len: the maximum length to copy.
 961  *
 962  * Returns the bytes copied <= len or a negative errno.
 963  */
 964 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
 965                              const void *src, size_t len)
 966 {
 967         return vringh_iov_xfer(wiov, (void *)src, len, kern_xfer);
 968 }
 969 EXPORT_SYMBOL(vringh_iov_push_kern);
 970 
 971 /**
 972  * vringh_abandon_kern - we've decided not to handle the descriptor(s).
 973  * @vrh: the vring.
 974  * @num: the number of descriptors to put back (ie. num
 975  *       vringh_get_kern() to undo).
 976  *
 977  * The next vringh_get_kern() will return the old descriptor(s) again.
 978  */
 979 void vringh_abandon_kern(struct vringh *vrh, unsigned int num)
 980 {
 981         /* We only update vring_avail_event(vr) when we want to be notified,
 982          * so we haven't changed that yet. */
 983         vrh->last_avail_idx -= num;
 984 }
 985 EXPORT_SYMBOL(vringh_abandon_kern);
 986 
 987 /**
 988  * vringh_complete_kern - we've finished with descriptor, publish it.
 989  * @vrh: the vring.
 990  * @head: the head as filled in by vringh_getdesc_kern.
 991  * @len: the length of data we have written.
 992  *
 993  * You should check vringh_need_notify_kern() after one or more calls
 994  * to this function.
 995  */
 996 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len)
 997 {
 998         struct vring_used_elem used;
 999 
1000         used.id = cpu_to_vringh32(vrh, head);
1001         used.len = cpu_to_vringh32(vrh, len);
1002 
1003         return __vringh_complete(vrh, &used, 1, putu16_kern, putused_kern);
1004 }
1005 EXPORT_SYMBOL(vringh_complete_kern);
1006 
1007 /**
1008  * vringh_notify_enable_kern - we want to know if something changes.
1009  * @vrh: the vring.
1010  *
1011  * This always enables notifications, but returns false if there are
1012  * now more buffers available in the vring.
1013  */
1014 bool vringh_notify_enable_kern(struct vringh *vrh)
1015 {
1016         return __vringh_notify_enable(vrh, getu16_kern, putu16_kern);
1017 }
1018 EXPORT_SYMBOL(vringh_notify_enable_kern);
1019 
1020 /**
1021  * vringh_notify_disable_kern - don't tell us if something changes.
1022  * @vrh: the vring.
1023  *
1024  * This is our normal running state: we disable and then only enable when
1025  * we're going to sleep.
1026  */
1027 void vringh_notify_disable_kern(struct vringh *vrh)
1028 {
1029         __vringh_notify_disable(vrh, putu16_kern);
1030 }
1031 EXPORT_SYMBOL(vringh_notify_disable_kern);
1032 
1033 /**
1034  * vringh_need_notify_kern - must we tell the other side about used buffers?
1035  * @vrh: the vring we've called vringh_complete_kern() on.
1036  *
1037  * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
1038  */
1039 int vringh_need_notify_kern(struct vringh *vrh)
1040 {
1041         return __vringh_need_notify(vrh, getu16_kern);
1042 }
1043 EXPORT_SYMBOL(vringh_need_notify_kern);
1044 
1045 MODULE_LICENSE("GPL");
/* [<][>][^][v][top][bottom][index][help] */
root/drivers/vhost/vringh.c

DEFINITIONS
